FEM-Based Numerical Analysis of a Shielded Interdigitated Capacitive Humidity Sensor
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Keywords:
Humidity Sensor, Capacitive Sensor, Interdigitated Electrodes, Polymer Dielectric, ANSYS Maxwell, Numerical Analysis, FEM SimulationAbstract
This study focuses on analyzing the humidity-dependent capacitive behavior of the sensor, driven
by a polymer dielectric layer whose permittivity is modulated by ambient relative humidity (RH). The
sensor's intricate architecture was meticulously modeled in 3D, incorporating a silicon substrate, copper
shielding layers, a silicon dioxide dielectric, and interdigitated copper electrodes embedded within the
humidity-sensitive polymer. The simulation methodology involved an electrostatic analysis with a 1 V
excitation applied to one set of interdigitated electrodes, while the other set and the shielding layers were
grounded to define the electric field. To systematically evaluate performance, a parametric sweep was
executed for RH, ranging from 0% to 100%. The principal results demonstrate a clear and highly linear
correlation between the sensor's capacitance magnitude and the RH, with an approximate change from 707
pF at 0% RH to 767 pF at 100% RH. This translates to a calculated sensitivity of approximately 0.6
pF/%RH, indicating effective detection of humidity variations. Furthermore, detailed field analyses of
electric field intensity, electric flux density, electrostatic potential, and stored energy density, visualized
across sensor surfaces and along a defined polyline, consistently confirmed the strategic concentration of
electric fields within the inter-electrode gaps. These findings validate the active sensing mechanism and
underscore the efficacy of the shielding layers in enhancing measurement stability. In conclusion, this
numerical investigation confirms the robust performance and design feasibility of the proposed shielded
interdigitated capacitive sensor for accurate and reliable humidity sensing applications.
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